Method of forming hard-rubber articles



J. F. JOHNSTON AND G. W. BULLEY.

7 METHOD OF FORMING HARD RUBBER ARTICLES.

APPLICATION FILED NOV. I2 i921.

Patented Nov. 14, 1922?,

UJI

all

' Invenivm' .Zo/m EJvImw Q Gear ,9

W13 ll 9774M Patented Nov. id, 1922..

T nears I JOHN F. JOHNSTON AND GEORGE BULLEY, OF'AKRON, OHIO, ASSIGNOBSTO THE MILLER RUBBER COMPANY, OF AKRON OHIO, A CORPORATION OF OHIO.

METHOD OF FORMING HARD-RUBBER ARTlIOLES.

Original application filed May 25, 1921, Serial No. 472,427. Divided andthis application fi led November 12, 1921. Qerial No. 514,706. i

To all whom it may concern:

Be it known that we, JOHN F. JoHNsToN and GEORGE W. BULLEY', citizens ofthe United States, and residents of Akron, Ohio, have invented certainnew and useful Improvements in Methods of Forming Hard- Rubber Articles,of which the following is a specification.

This application is a division of an application filed by us in theUnited States Patent Cities on the 25th of May, 1921, No. 472,427. I

Our present invention relates .to improvements in rubber articles orcontainers and is designed more especially for storage battery cellconstruction, and is so described although not limited to such use, andcomprises a new method of manufacture as hereinafter described anddefined by the appended claims. I

Heretofore, so far as we are aware, storage batteries as commerciallyconstructed have comprised a plurality of separate or individual hardrubber cells set in a wooden box and surrounded by an asphaltumcomposition. Such assembled form is expensive and unreliable, but theconstruction of a unitary article has heretofore been foundimpracticable due to moulding difficulties.

The present invention aims to provide a method by which such unitaryarticle may be moulded in an inexpensive and expeditious manner tosecure thereby a resulting article which will be light in weight butstrong and durable and which will be acid proof and an excellent heatinsulator.

We have discovered thatby incorporating in a hard rubber vulcanizingcompound a blowing agent capable of being volatilized by the vulcanizingheat, such hard rubber compound could be used for cell wall and bottomconstruction and when vulcanized would, while being hard and rigid, havea cellular formation which would make it extremely li ht and ofexcellent heat insulating .quality. Various blowing agents may be of thecontainer causes the interior of the cell walls to be practically void,thereby making such walls a. still better heat insulator.

Various modifications of the container structure and of the method ofmaking the same have been discovered by us in the course of ourinvestigation, aswill hereinafter appear.

.In order that our invention may be more easily understood, we willdescribe the same in connection with the accompanying drawings, inwhich: v

Figure 1 is a longitudinal vertical section through the container withthe forming mould box indicated in dotted lines. 4

a Figure 2 is a section on line 2-2 of Figure 1.

Figure 3 is an enlarged sectional view of cell wall forming material.

Figure 4% is a longitudinal vertical section through the mould box withthe cores 7 in place.

Fgure 5 is a transverse view through the same.

Figure 6 is a top plan view of the moul box, partly in section, and

' Figure 7 is a perspective detail of one of the core members. v

A container constructed in accordance with our invention is illustratedin inverted position at 1 in Figures 1 and 2, in which it is shown as aunitary battery cell having transverse partitions 1 forming with theside and end walls a plurality of compartments or cells a, w, a, (threebeing shown as an example of any desired numher.) The bottom 1 isprovided with the customary cross bridges or ribs 6 for supporting theusual plates (not shown) clear of the bottom, and the edges of the sideand end walls and partitions are preferably rebated, as indicated at oanda to receive individual cover plates (not shown). The side and endwalls and bottom are constructed of vulcanized hard rubber compound, oneor more of the surfaces, preferably both, being of dense rubber, asindicated at m and 00' and the intermediate portion being of cellularformation as indicated at y, the whole being integrally united. I

Accordingto one manner of carrying out our invention, we provide a metalmould 2 comprising side, end and bottom and top walls detachablyconnected together as shown, the bottom having core projections 2 formedto giveproper shapeto the cell cavities, and such core. parts beingprcferably detachably connected to the bottom member, whereby they aremore easily handled. The projections are'covered or wrappedwith thinlayers or sheets of hard rubber vulcanizing compound such as indicatedat w, and, if separated from the bottom member, are reattached thereto.The side and end walls of the mould are then secured together and to thebottom plate, and if the container is to have a smooth dense exterior,said side and end mould would also be covered with sheets or layers ofhard rubber compound .70.

The intervening space is then partially filled with the hard rubbercompound 2 having the blowing agent incorporated therein.

This ma be put in sheet or slab form, as,

owing to t e expansion taking place in vulcanizing there will be ampleroom to permit the slab containing the blowing agent to be slid orinserted edgewise into place. The container bottom may then be appliedin the same way, to wit, by inserting the bridge forming pieces in thecore grooves, laying a sheet of rubber over the core ends and applyingthereon the layer or slab containing the blowing agent, upon which maybe applied an, outer la er for forming a smooth outer surface.hereafter. the mould is closed and subjected to vulcanizing heat in anysuitable manner. This vulcanizing heat volatilizes the blowing agent andexpands the rubber producing therein a cellular structure, and causesthe mould cavity to be completely filled and a complete integral Iunitary article having a rigid cellular formation occupying a greater orless portion of its wall space depending on the relative thickness andarrangement of the sheets.

As a modification of this process, layers of hard rubber compound withand without blowing agent respectively, could be assembled orsuperimposed to form a composite slab which could then be applied to thecore members.

Another modification which we have found advantageous is to assemble thelayers over a temporary form and thereafter transfer the same to themould, thereby permitting the moulds to be kept in more constant use andefi'ecting a saving in mould. equipinent.

consists in building the uncured article on a core ofalternate layers ofblower-containing and ordinary hard rubber compound, placing the coreand article in a rigid mould having a greater volume than that of thecoreand uncured article, and applying heat to release the blowing agentwhereby the article is expanded to the size of the mould and vulcanizedtherein.

3. The process of making an article partly of cellular and partly ofnon-cellular rigid I construction which consists in introducing into aclosed mould blower containing and non-blower containing layers of hardrubber compounds, and heating the mould whereby the blower-containingcompound is changed to a cellular formation and exerts 'confinmgpressure against the layer of non-blower containing compound, and bothcompounds are vulcanized together.

4:. The process of exerting pressure upon a layer of rubber compound ina closed mould to form the same, which consists in introducing'in thesame mould a layer of a similar compound containing a blowing agent andcausing the blower containing stock to expand by applying heat wherebythe two compoundsare simultaneously vulcanized.

5. The hereindescribed process which consists in assemhbling twosegregated batches or portions of hard rubber compound, one containing ablowing agent, and vulcanizing the same in a closed mould.

In testimony whereof, we affix our signatures.

JOHN F. JOHNSTON. GEORGE W. BULLEY.

